In this section, you want to be able to choose between using a specific albedo map or a simple color value, which will allow you to rapidly prototype materials by specifying a simple value to get the correct albedo. You can then bring that value through to Photoshop as a base for your final albedo map. This will also apply to the Roughness Setup section of this tutorial.
As stated previously, this setup allows you to choose between using an albedo map or a color value for your base color. You choose between the two by using the static switch parameter called UseDiffuseMap? in your instanced material. If this is set to true, you can then use the input a specific albedo texture, and this is multiplied with a DiffTint constant value which allows you to tint the color of the specified albedo map. If you do not use an albedo map, you can define the albedo value using DiffuseValue.
To the left of the DiffMap texture input, you can see that a node has been plugged into the UV slot. This connects to the Parallax part of the master material. You could add a UV tiling setup into this as well, which would allow you to control the tiling of your material in UE4 rather than in your 3d modeling package.
The following example shows the flexibility of this system. On the left, the material is using a single color for the albedo map. In the middle, it is using just an albedo map. On the right, it is using an albedo map that has been tinted orange. This shows how you can use the same maps to get a lot of variety in the engine.
Single Color for the Albedo Map
Albedo Map with Color